Sustained release pharmaceutical preparation using diffusion barriers whose permeabilities change in response to changing pH
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United States of America Patent
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Apr 7, 1992
Grant Date -
N/A
app pub date -
Oct 5, 1990
filing date -
Oct 5, 1990
priority date (Note) -
Expired
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Abstract
A sustained-release pH independent pharmaceutical preparation having multi-units of microparticles comprising a granular drug which is less soluble at low pH and more soluble at high pH. The granular drug is surrounded by or admixed with a pH controlled material formed from at least one polymer that is hydrophilic at low pH and hydrophobic at higher pH and is in a ratio with the granular drug such that the resulting sustained-release pharmaceutical preparation is independent from the pH environment. The resulting sustained-release pH independent pharmaceutical preparation allows a uniform release of drug for a period of at least 12 to 24 hours. In an alternative embodiment, the drug may be more soluble at low pH and less soluble at higher pH and the pH controlled material formed from at least one polymer that is hydrophobic at low pH and hydrophilic at higher pH.
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